The invention concerns a filtration unit for the selective separation of materials from fluids by porous membrane adsorbers, and finds application in the fields of biotechnology, genetic procedures, pharmaceuticals, food and beverage industries and in environmental operations, ranging in scale from laboratory work to commercial production.
The invention is especially useful in the selective separation and purification of materials which have specific adsorption characteristics, such as bio-specific molecules, proteins, enzymes, ionizable substances and metal ions, particularly those of heavy metals. According to PCT patent application Ser. No. 92/00805, porous membrane adsorbers carry on their surfaces functional groups, ligands, interwoven fibers, or reactants capable of interaction with at least one substance in contact therewith in a fluid phase, which moves through the membrane by gravity. The term "membrane adsorber" is understood in the art as a general term for membrane ion-exchangers, ligand membranes and activated membranes. A membrane adsorber is classified according to the particular functional group, ligand or reactant carried on or in its surface.
U.S. Pat. No. 4,895,806 discloses a filtration unit for the separation of molecular components from fluid mixtures by membrane adsorbers, comprising a housing, a plurality of membrane discs separated into groups by washers, with the entire membrane disc assembly being compressed between compression rings, wherein the peripheries of the compression rings and washers are in contact with the wall of the housing so as to provide a seal to prevent leakage between the membranes and the housing wall. The disadvantages of such a design are (1) when a smaller number of membrane adsorber discs are used, the unit's adsorption capacity is too low, and (2) when a greater number of membrane discs are used, the unit suffers from an exponentially restricted flow rate, even at higher pressures.
It is therefore a principal object of the present invention to provide a membrane adsorber filter having a large adsorption capacity and large flow rates, which is capable of scale up, and which does not require a housing.
The foregoing and other objects, features, and advantages of the invention will be more readily understood upon consideration of the invention which is summarized and described in detail below.